O2 sensor bias

[Jason Weir]

Alex Samson wrote:

> A question that has remained unanswered in my head for many years now
> is
> if the O2 sensor outputs 0.45v at 14.7 mix,  what is the mix ratio
> when
> it outputs 0.8v? or 0.9v? or 0.2v?  Does anyone have a graph of a
> common
> O2 sensor characteristic of Voutput vs Fuel ratio? I have searched for
>
> Bosch data on this but have never seen it.

Below is a snip from Bruce Plecan's tuning tips located at
http://efi332.eng.ohio-state.edu/diy_efi/oem/gm/tunetip.html

snip,
>From some personnel notes from the early-mid 80's there were many 2 gas
analyzers that went to market for the then pending
inspections for CA. Here are some conclusions drawn from some GM
training center notes and a Radio Shack engine book.
First from a slip of paper, circa '83, that lists O2 sensor volts
relative to AFR Air Fuel Ratio, and one from 2-3 years ago from
Cyberdyne, who manufacturers a 10 led AFR Monitor. The voltages match
i.e.: 1v=17:1; .3v=16; .5v=14.9 ; .7v=13.8:1;
.9v=12.7:1. Also, going by the RS book are some differences in response
time vs temp, and differences in sensor voltage
depending on load. So yes there are variables, and yes the results will
vary with mounting locations, and loading. But for high
performance tuning as an INDICATOR, there are no reservations on using
one as a guide. The double check would be doing
plug cuts. If you are working on a 20:1 AFR engine, then you would have
to use a wide ratio O2 sensor, or if it was exposed
to a limited amount of exhaust gas and needed heating and thermal
compensation then you need the double wammy wide ratio
O2 stuff. For what the average DIY will be attempting, a good ole GM
single wire mounted in iron manifold, and a 3 wire used
in tubular headers will work just fine. So while the ME's, and EE's
discuss the merits of both for a lot of us just building the 10
LED O2 monitor like is shown in the GN T-type tech area will work fine
(http://ni.umd.edu/gnttype/www/buick.html). Also, the
GN's have a bunch of cars running 10s,11s, that regularly use unleaded
with a heated O2 and have "fair results" (10s with A/C
actually is better than fair in my book).
--
Jason Weir
88 Wrangler - 258 Chevy TBI
Fayetteville, North Carolina
http://home.att.net/~jweir/tbi/inject.htm  --- TBI Installation Page
http://home.att.net/~jweir/resume.htm      --- My Resume
mailto:jweir at worldnet.att.net